RFR: 1234: Caching Maven repo

Thu Oct 8 20:48:26 UTC 2020

So this adds the caching of Maven dependencies we discussed in the other PR. While testing this in my fork, it reduced
the build time from ~30 min to ~23 min. I'll reword the commit message if there's agreement on this and a Jira issue
exists. Thanks!

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Commit messages:
 - 1234: Caching Maven repo

Changes: https://git.openjdk.java.net/jmc/pull/124/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=124&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-1234
  Stats: 18 lines in 1 file changed: 18 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/124.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/124/head:pull/124

PR: https://git.openjdk.java.net/jmc/pull/124